Today's consumer electronics market frequently demands complex functions requiring very intricate circuitry. Scaling to smaller and smaller fundamental building blocks, e.g. transistors, has enabled the incorporation of even more intricate circuitry on a single die with each progressive generation. The need for ever more sophisticated packaging for such a semiconductor die, or groups of semiconductor dice, has paralleled the scaling, increasing the technological demands on semiconductor packages which house such semiconductor die or groups of semiconductor dice.
Implementing thin core/coreless substrates within the framework of a current electronic packaging assembly process (e.g., a process involving bulk heating and cooling of the semiconductor package) without significant yield loss is a big challenge. For example, the yield loss may be due to issues associated with package warpage, which is significantly modulated during any polymer curing (including underfill) process. Currently, the underfill curing process requires subjection of an entire package to a thermal cycling, which can exacerbate the overall warpage of the package.
In another example, polymer shrinkage that arises as a result of subjecting a polymer composite to a thermal cycle during the curing of the polymer leads to reliability concerns such as delamination and cracking at different interfaces associated with an underfill or polymer thermal interface material (PTIM) within a semiconductor package. Currently, there is no predictable way to control the cure kinetics of such a composite system.
Furthermore, current polymer composite formulations have temperature dependent viscosity, which makes it difficult to tailor the viscosity for improved pot life along with improved flow during dispense. An ideal system could have the same viscosity at storage temperatures and at the dispense temperature, which would aid with tailoring polymer composite materials for use in electronic packaging. One approach to reducing viscosity of the underfill has been to reduce the filler content. However, this approach negatively impacts the mechanical properties of the underfill material, including undesirably impacting the coefficient of thermal expansion (CTE) and the modulus of the underfill material.